There is a technology referred to as thin provisioning such as that disclosed in JP 2003-15915 A (Patent Document 1). The thin provisioning is a technology for allocating virtual volumes to a host computer. The virtual volumes are volumes to which data storage areas are allocated from pooled physical disks only after the host computer writes data in the virtual volumes.
There is a server virtualization technology for constructing a plurality of virtual machines (VMs) on one host computer. In the server virtualization technology, a technology disclosed in “VMware Virtual Machine File System: Technical Overview and Best Practices” (Non-patent Document 1) is utilized. According to this technology, a hypervisor that is a management program of server virtualization centrally manages a plurality of volumes to provide a single data storage area to an administrator.